Apparatus for regulating the tension of warp threads in power looms

ABSTRACT

A power loom wherein a dancer roll is urged against warp threads between the warp beam and the weaving station. The dancer roll engages the upper sides of the warp threads in a space between two cylindrical guides which engage the undersides of the warp threads. The dancer roll is urged against the warp threads with a constant force by two double-acting hydraulic cylinders whose upper chambers receive a pressurized hydraulic fluid from a pump through a conduit which contains an adjustable pressure regulating valve, a pressure accumulator and a check valve. A further valve is provided to connect the upper chambers with the tank while connecting the lower chambers of the cylinders to the pump so that the dancer roll rises above the guides to permit for convenient introduction of warp threads into the loom. The position of the dancer roll is monitored by a fluid flow regulating device which can adjust a variable-delivery pump for a variable-speed hydraulic motor which rotates the warp beam in a direction to pay out warp threads.

United States Patent [1 1 Bassing et al.

[ July 8,1975

[73] Assignee: ALFA-LAVAL Bergedorfer Eisenwerke GmbH, Hamburg,

Germany [22] Filed: Dec. 11, 1973 [21] Appl. No.: 422,937

[30] Foreign Application Priority Data Dec. 12, 1972 Germany 2260607[52] US. Cl 139/110; 242/7553 [51] Int. C1. D03D 49/06; D03D 49/10 [58]Field of Search 139/110, 109, 97, 99, 114, 139/115; 242/755, 75.53;66/86 A FOREIGN PATENTS OR APPLlCATlONS 462,063 10/1968 Switzerland139/110 371,406 9/1963 Switzerland 139/110 1,099,725 1/1968 UnitedKingdom 139/1 10 Primary Examiner-James Kee Chi Attorney, Agent, orFirm-Michael S. Striker [57] ABSTRACT A power 100m wherein a dancer rollis urged against warp threads between the warp beam and the weavingstation. The dancer roll engages the upper sides of the warp threads ina space between two cylindrical guides which engage the undersides ofthe warp threads. The dancer roll is urged against the warp threads witha constant force by two double-acting hydraulic cylinders whose upperchambers receive a pressurized hydraulic fluid from a pump through aconduit which contains an adjustable pressure regulating valve, apressure accumulator and a check valve. A further valve is provided toconnect the upper chambers with the tank while connecting the lowerchambers of the cylinders to the pump so that the dancer roll risesabove the guides to permit for convenient introduction of warp threadsinto the loom. The position of the dancer roll is monitored by a fluidflow regulating device which can adjust a variable-delivery pump for avariable-speed hydraulic motor which rotates the warp beam in adirection to pay out warp threads.

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APPARATUS FOR REGULATING TENSION OF WARP THREADS IN POWER LOOMSBACKGROUND OF THE INVENTION The present invention relates to apparatusfor regulating the tension of warp threads in power looms.

German Pat. No. 1,535,332 discloses an apparatus which monitors thetension of warp threads in a loom between the warp beam and the leaserods. The apparatus employs a dancer roll which is biased against thewarp threads by springs and is mounted on a movable supporting rod whichcooperates with a detector. The rate at which the warp beam pays out thewarp threads is determined by the detector in dependency on the positionof the dancer roll. A drawback of the patented apparatus is that eachchange in the position of the dancer roll entails a change in the biasof springs and hence an automatic change in the tension of warp threads.Also, the regulation of tension is of the followup type, i.e., the speedat which the warp beam pays out the warp threads is changed only afterthe tension of warp threads has already been changed so that the actualtension deviates from a desirable optimum tension. Furthermore. thepatented apparatus is capable of monitoring the tension of some but notall of the warp threads in a power loom.

In the making of certain fabrics, such as fourdrinier wire for use inpaper making machines, the setting of filling and warp threads is ofutmost importance. Even minor deviations from an optimum density offilling and/o'r warp threads can adversely affect the quality of suchproduct in contrast to many other types of fabrics wherein the exactsetting of threads is of no particular importance. In order to insure asatisfactory setting of filling threads, the warp threads and thegrowing fabric must be moved through a predetermined distance uponcompletion of each working cycle to thus insure that i the tension ofthe warp threads as well as the tension of the fabric remains unchangedand matches an optimum tension.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved apparatus for regulating the tension of warp threadsin a loom in such a way that the tension of all warp threads remainsconstant and is not dependent on the regulation of withdrawal of warpthreads from the warp beam or beams.

Another object of the invention is to provide the apparatus with simpleand inexpensive but reliable means for tensioning all of the warpthreads between the warp beam or beams and the station where the warpthreads are interwoven with filling threads.

An additional object of the invention is to provide novel and improvedmeans for monitoring the position of the device which biases the warpthreads with a constant force irrespective of the rate of withdrawal ofwarp threads from the warp beam or beams.

A further object of the invention is to provide novel and improved meansfor changing the speed of angular movement of one or more warp beams inresponse to changes in the position of the warp biasing and tensioningdevice.

The invention is embodied in a power loom which comprises at least onerotary warp beam, variablespeed prime mover means (e.g., a hydraulicmotor) which can rotate the warp beam in a direction to pay mi wllwmmwli dfl-lld muh tar-madma lama.iwsmmdhp.huuumsnusnzral .11

out warp threads (the connection between the prime .mover means and theshaft of the warp beam may comprise a worm drive), means for collectingthe fabric which is being formed by interweaving the warp .threads withfilling threads at a weaving station, a pair of spaced apart guideswhich engage the undersides of warp threads between the warp beam andthe weaving station, a displaceable biasing element (preferably a dancerroll) which engages the upper sides of warp threadsbetween the twoguides, means for adjusting the speed of the prime mover means inresponse to displacement of the biasing element (such displacementnormally indicates that the warp threads are not being paid out at theexact rate at which the fabric is being formed), and tensioning meansfor urging the biasing element against .the warp threads with apredetermined but variable constant force so that the tension of warpthreads remains unchanged irrespective of displacements of the biasingelement. The tensioning means comprises one or more fluid-operateddisplacing devices (preferably double-acting hydraulic or pneumaticcylinders) which areoperatively connected with the biasing element andmeans for supplying to the displacing devices a pressurized, hydraulicor pneumatic fluid at a constant pressure. Such means for supplyingpressurized fluid may include a pump which supplies a stream ofpressurized fluid, conduit means connecting the pump with a chamber ofeach displacing device whereby the fluid in such chamber causes thecylinder or the piston of the respective displacing device to urge thebiasing element against the warp threads, and a preferably adjustablepressure regulator in the conduit means.

The novel features which are considered as characteristic-of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic sectional view ofa power loom which embodies the improved apparatus for regulating thetension of warp threads;

FIG. 2 is a view as seen in the direction of arrow I] in FIG. 1, furthershowing the details of the means for applying a constant force to theelement which biases the warp threads;

FIG. 3 is a perspective view of a monitoring unit for the position ofthe biasing device; and

FIG. 4 is a diagram showing the operative connection between themonitoring unit and the prime mover means for the warp beam.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a portion of apower loom whose frame or housing includes an upright wall 1 whichsupports a rotary crankshaft 2 for an arm 3 which reciprocates a sword 4for a sley 5 and a reed 6 through which pass the warp threads 7. Thewoven fabric 8 is pulled by three collecting beams 9a, 9b, which arecontrolled by a suitable regulator (not shown) so that the fabric isshifted through identical distances. A dobby machine (not shown) movesthe shafts 10a, 10b with heddles 11a, llb having eyes for warp threads 7to form the shed 12 through which the filling thread is passed by meansof a shuttle (not shown). The parts a, 10b, 1 la, 1 lb are located at aweaving station.

At the rear side of the wall 1, there are provided two cylindricalsupporting elements or guides 13, 14 for warp threads 7 which aresupplied by a warp beam 15 having a shaft 19 journalled in bearings 19aand provided with a worm wheel 20 mating with a worm 21. The worm 21 ismounted on a worm shaft 21a which is driven by a variable-speed primemover here shown as a hydraulic motor 22.

The warp threads 7 which are trained over the two spaced-apartcylindrical supporting elements or guides 13, 14 are further engaged bya biasing element here shown as a dancer roll 16 which is carried by(i.e., rests on) the threads 7 and bears against the warp threads due toits own weight as well as due to the force applied by a motiontransmitting member 17 between the shaft of the dancer roll 16 and thepiston rods 18a of two hy draulic displacing cylinders 18 mounted in theframe of the loom. The diameter of the dancer roll 16 almost equals oris only slightly less than the distance between the cylindrical guides13, 14. The guides engage the undersides and the dancer roll engages theupper sides of the threads 7.

As shown in P16. 2, the cylinders 18 are of the double-acting type andtheir piston rods 18a are articulately connected to the motiontransmitting member 17. The lower ends of the cylinders 18 are connectedto a stationary support 118 of the frame. The pistons 18b separate theinternal spaces of the respective cylinders 18 into upper and lowerchambers 18c, 18d which are respectively connected with conduits 30 and31. The conduits 30, 31 are connected with a fluid flow regulating valve48 having an inlet port connected to the pressure outlet of a hydraulicpump 24 driven by an electric motor 23. An outlet port of the valve 48is connected to a tank 48a for the pump 24. The parts 23, 24 togetherconstitute a source of pressurized hydraulic fluid.

The conduit 30 contains a check valve 26 which prevents hydraulic fluidfrom flowing from the upper cylinder chambers 18c into the tank 48a, anadjustable pressure regulator valve which is mounted in a branch line30a, a pressure accumulator 29 serving as a pressure fluid reservoir, apressure gauge 28 and a safety valve 27 for the accumulator 29.

The pressurized hydraulic fluid which is supplied by the pump 24 andflows through the regulating valve 48 and check valve 26 tends to urgethe pistons 18b downwardly, as viewed in FIG. 2, with a constant forceindependently of the position of the dancer roll 16 so that the lattersubjects the warp threads 7 to a constant tension of unvaryingmagnitude. As shown in P10. 2, the dancer roll 16 may comprise severalcoaxial cylindrical sections 16a, 16b, 16c mounted on a common shaft 16dwhich is joumalled in bearing brackets 17a of the motion transmittingmember 17. The number of sections of the dancer roll 16 depends on thewidth of the power loom.

By changing the position of the valve member in the regulating valve 48,one can admit pressurized fluid into the conduit 31 so that suchpressurized fluid flows into the lower chambers 18d of the displacingcylinders 18 to thereby move the dancer roll 16 upwardly, for example,to the position 16A shown in FIG. 1 by phantom lines. This allows forconvenient threading of warp threads 7 through the loom. The strokes ofthe pistons 18b are selected with a view to insure that the dancer roll16 can be displaced from a level below to a level above the guides 13,14, and the uppermost position 16A of the dancer roll 16 is such thatthe dancer roll does not interfere with the introduction of warp threads7 through the space between the guides 13, 14 and the dancer roll. Whenthe chambers 18c are connected with the pump 24, the piston rods 18apull the dancer roll 16 against the upper sides of the warp threads 7.

FIG. 3 illustrates a presently preferred embodiment of means formonitoring the position of a relatively short (single-section) dancerroll 116 which is mounted on a slightly modified motion transmittingmember 117 and is urged against the warp threads (not shown) by the twodouble-acting hydraulic displacing cylinders 18 substantially in thesame way as illustrated in FlG. 2. The member 117 has a laterallyextending bracket or holder 32 for a pin 33 which is received in thebifurcated arm 34b of a two-armed lever 34. The latter is fulcrumed at35 on a bracket 36 in the frame of the loom. The other arm 34a of thelever 34 constitutes or includes a gear segment in mesh with a spur gear37 on the shaft of a fluid flow regulating device 38.

P16. 4 shows the connection between the regulating device 38 and thevariable-speed hydraulic motor 22 for the warp beam 15. Avariable-delivery hydraulic pump 39 is provided to supply apredetermined quantity of pressurized fluid to the hydraulic motor 22through a check valve 40 when the loom is in use. The motor 22 suppliesa stream of fluid to a conduit 41 which discharges into a tank 42. Theflow of fluid to and from the motor 22 is controlled by a valve 248. Theflow regulating device 38 is connected with a doubleacting adjustingcylinder 45 by conduits 43, 44. The piston 46 of the cylinder 45 isconnected with a piston rod 46a which can regulate the delivery of thepump 39 by means of a linkage 47.

The exact details of the regulating device 38 and variable-delivery pump39 form no part of the invention. Such components are of thecommercially available type.

When the loom is in use, the collecting beams 9a, 9b, 9c draw the fabric8 through distances corresponding to the density of the setting of thefilling while the motor 22 rotates the worm shaft 21a to unwindpredetermined unit lengths of warp threads 7 from the beam 15. lf themotor 22 reduces the unit lengths of warp threads 7, i.e., to less thanis necessary in view of the length of fabric which is being produced onintroduction of a filling thread, the dancer roll 16 rises toward thesupporting elements or guides 13, 14 whereby the motion transmittingmember 17 pivots the lever 34 clockwise, as viewed in FIG. 3, and thegear segment 34a changes the angular position of the shaft of theregulating device 38. The latter changes the position of the piston 46in the adjusting cylinder 45 so that the linkage 47 adjusts thevariable-delivery pump 39. The pump 39 changes the rotational speed ofthe motor 22 so that the latter causes the beam 15 to discharge warpthreads 7 at a higher rate and the dancer roll 16 descends back towardits normal position.

If the rate at which the motor 22 allows the beam 15 to pay out warpthreads 7 increases beyond that which is needed in view of the rate offabric growth, the dancer roll 16 descends and the member 17 pivots thelever 34 in a counterclockwise direction, as viewed in FIG. 3, so thatthe regulating device 38 causes the cylinder 45 to adjust the pump '39in order to reduce the rotational speed of the motor 22. This causes thedancer roll 16 to rise back toward-its normal position.

By appropriate design of the linkage 47, one can select in advance theaverage delivery of the pump 39 as well as the extent of changes in therate of delivery when the position of the'piston 46 in the cylinder 45changes to a given extent.

The apparatus of the present invention allows the dancer roll 16 tochange its position from (i.e., to float up and down beyond) a neutralor normal position within a relatively long interval of time. However,the tensioning of warp threads 7 remains unchanged because the roll 16is biased against the upper sides of such threads with a constant force.When the loom is started, the motor 23 begins to drive the pump 24 sothat the valve 48 supplies pressurized fluid to the conduit 30 via checkvalve 26 whereby such fluid enters the upper chambers 18c of thedisplacing cylinders 18. The fluid pressure in the chambers 18c isdetermined by the setting of the adjustable pressure regulating valve soas to insure that the piston rods 18a pull the dancer roll 16 downwardlyand the dancer roll 16 biases the warp threads 7 with a selected force.When the pressure of fluid in the chambers 18c reaches the selectedvalue, the pressure regulating valve 25 opens and dischargesadditionally supplied fluid into the tank 82 via conduit means 31. Thevalve 25 closes as soon as the fluid pressure in the chambers 18c dropsbelow the preselected value and the fluid delivered by the pump 24 thenflows into the chambers 180 to restore the preselected bias upon thewarp threads 7.

An important advantage of the improved tensioning apparatus is that thebias of the dancer roll 16 upon the warp threads 7 remains constant evenif the roll 16 moves up or down and independently of the speed of themotor 22 for the warp beam 15. The bias of the dancer roll 16 isdetermined exclusively by the setting of the adjustable valve 25 in theconduit 30 which normally supplies pressurized fluid to the cylindercham' bers 18c. Since the distance between the guides l3, l4 equals orapproximates the diameter of the dancer roll 16, the stretches 7a, 7b ofthe warp threads 7 are substantially parallel to each other. This alsocontributes to the fact that the displacements of dancer roll 16 do notalter the tension of warp threads.

The improved apparatus is susceptible of many additional modifications.For example, the hydraulic means for urging the dancer roll 16 or ananalogous biasing element against the warp threads 7 can be replaced bya pneumatic system without departing from the spirit of the invention.Moreover, the monitoring means of F l6. 3 can be replaced by apneumatically, electrically, magnetically or otherwise operated detectorsystem for the position of the dancer roll 16 or an analogous biasingelement for the warp threads 7. Still further, the adjusting means 39,45, 46, 46a, 47 for the variable-speed motor 22 can be replaced bypneumatic, electric, electromagnetic or other speed regulating means.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge.readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of our contribution to the art and,

6 therefore, such adaptations shouldandare intended to be comprehendedwithin the-meaning and range of equivalence of the claims. 1 w

What is claimed as new and desired tobe protected by Letters Patent isset forth in the appended claims:

l. In a power loom, a combination comprising a frame; at leastone rotarywarp beam; a variable-speed hydraulic motor for rotating said warp beamin a direction to pay out warp threads; means for collecting the fabricobtained by interweaving said warp threads with filling threads at aweaving station; and ah arrangement for regulating the let-off of thewarp threads with constant warp thread tension, said arrangementcomprismg:

a. a pair of spaced-apart guides located between said warp beam and saidweaving station and arranged to engate one side of each warp thread,

b. a displaceable dancer roll resting in a bight of the warp threadsbetween said guides and engaging the other side of each warp thread,

c. a support member rotatably supporting said dancer roll,

d. hydraulic cylinders connecting said support member to said frame andeach having a piston reciprocably therein and defining at least onepressure chamber,

e. conduit means connecting each pressure chamber to a source ofpressurized hydraulic fluid for urging said dancer roll against the warpthreads,

f. an adjustable constant pressure regulating valve connected to saidconduit means for maintaining a constant pressure in said pressurechambers irrespective of the position of said dancer roll, and

g. regulating means continuously actuated by said support member foradjusting the flow of pressurized hydraulic fluid to said hydraulicmotor in response to displacement of said dancer roll.

2. A combination as defined in claim 1, wherein said dancer rollcomprises a plurality of coaxial cylindrical sections.

3. A combination as defined in claim 1, wherein the diameter of saiddancer roll equals or is slightly less than the distance between saidguides.

4. A combination as defined in claim 1, and further comprising avariable-delivery hydraulic pump connected to said hydraulic motor, saidregulating means being operatively connected with said support memberand said hydraulic pump for chaning the delivery rate of said pump inresponse to displacement of said support member.

5. A combination as defined in claim I, wherein said source of pressurefluid comprises a second hydraulic pump, said conduit means connectingsaid pressure chambers to said second hydraulic pump, and a pressureaccumulator connected to said conduit means between said pressurechambers and said second hydraulic pump.

6. A combination as defined in claim 5, further comprising a check valvein said conduit means between said second hydraulic pump and saidconstant pressure regulating valve to prevent pressurized hydraulicfluid from flowing towards said second hydraulic pump.

7. A combination as defined in claim 5, wherein said hydraulic cylindersare double-acting cylinders and each comprising a first and and apressure chamber separated by said piston, and including a hydraulictank, said conduit means comprising a first conduit connected with saidfirst chambers and a second conduit connected with said second chambers,and including a reversing valve connected to said conduits and movablebetween two positions in one of which it connects said first chambers tosaid second hydraulic pump and said second chambers to said tank and inthe other of which it connects said first chambers to said tank and saidsecond chambers to said second hydraulic pump.

8. A combination as defined in claim I, wherein said hydraulic cylindersare connected to said frame and said pistons are provided with pistonrods articulatedly pressure chambers to said hydraulic tank.

1. In a power loom, a combination comprising a frame; at least onerotary warp beam; a variable-speed hydraulic motor for rotating saidwarp beam in a direction to pay out warp threads; means for collectingthe fabric obtained by interweaving said warp threads with fillingthreads at a weaving station; and an arrangement for regulating thelet-off of the warp threads with constant warp thread tension, saidarrangement comprising: a. a pair of spaced-apart guides located betweensaid warp beam and said weaving station and arranged to engate one sideof each warp thread, b. a displaceable dancer roll resting in a bight ofthe warp threads between said guides and engaging the other side of eachwarp thread, c. a support member rotatably supporting said dancer roll,d. hydraulic cylinders connecting said support member to said frame andeach having a piston reciprocably therein and defining at least onepressure chamber, e. conduit means connecting each pressure chamber to asource of pressurized hydraulic fluid for urging said dancer rollagainst the warp threads, f. an adjustable constant pressure regulatingvalve connected to said conduit means for maintaining a constantpressure in said pressure chambers irrespective of the position of saiddancer roll, and g. regulating means continuously actuated by saidsupport member for adjusting the flow of pressurized hydraulic fluid tosaid hydraulic motor in response to displacement of said dancer roll. 2.A combination as defined in claim 1, wherein said dancer roll comprisesa plurality of coaxial cylindrical sections.
 3. A combination as definedin claim 1, wherein the diameter of said dancer roll equals or isslightly less than the distance between said guides.
 4. A combination asdefined in claim 1, and further comprising a variable-delivery hydraulicpump connected to said hydraulic motor, said regulating means beingoperatively connected with said support member and said hydraulic pumpfor chaning the delivery rate of said pump in response to displacementof said support member.
 5. A combination as defined in claim 1, whereinsaid source of pressure fluid comprises a second hydraulic pump, saidconduit means connecting said pressure chambers to said second hydraulicpump, and a pressure accumulator connected to said conduit means betweensaid pressure chambers and said second hydraulic pump.
 6. A combinationas defined in claim 5, further comprising a check valve in said conduitmeans between said second hydraulic pump and said constant pressureregulating valve to prevent pressurized hydraulic fluid from flowingtowards said second hydraulic pump.
 7. A combination as defined in claim5, wherein said hydraulic cylinders are double-acting cylinders and eachcomprising a first and and a pressure chamber separated by said piston,and including a hydraulic tank, said conduit means comprising a firstconduit connected with said first chambers and a second conduitconnected with said second chambers, and including a reversing valveconnected to said conduits and movable between two positions in one ofwhich it connects said first chambers to said second hydraulic pump andsaid second chambers to said tank and in the other of which it connectssaid first chambers to said tank and said second chambers to said secondhydraulic pump.
 8. A combination as defined in claim 1, wherein saidhydraulic cylinders are connected to said frame and said pistons areprovided with piston rods articulatedly connected to said supportmember.
 9. A combination as defined in claim 1, wherein said hydrauliccylinders pull said dancer roll downwardly against the upper side of thewarp threads.
 10. A combination as defined in claim 7, wherein saiddancer roll is normally located at a level below said guides and saidhydraulic cylinders are adapted to move said dancer roll to a levelabove said guides by operating said reversing valve to connect saidsecond pressure chambers to said hydraulic pump and said first pressurechambers to said hydraulic tank.